There is a general desire for people to have white teeth. Such white teeth are an indication of a good health and in particular good oral care health. A problem is that various foods and the use of tobacco will discolor teeth. Beverages such as coffee, tea and cola beverages can discolor teeth.
As a result various products and procedures have been developed to whiten teeth. These products and procedures are either purchased and/or used directly by the consumer or are applied by a dentist or other professional. The more effective products and procedures are those that are performed by a dental professional.
Typically this consists of the dental professional forming a dental tray from an impression of a persons teeth. The dental tray is formed by any by any of the well known and well used procedures. After the dental tray is formed to the structure of the teeth a whitening formulation is placed in the tray and the tray placed into the mouth and against the teeth to be treated. The tray with the whitening composition in home use typically is left in the mouth for from about 10 minutes to several hours; ie. up to 12 or more hours. If the treatment is only in the dental office the time of the treatment typically will be from about 0.5 hour to about 2 hours.
The products used solely by consumers primarily comprise whitening strips and brush-on products. Whitening strips are plastic strips with the whitening formulation on one surface. The surface with the whitening formulation is pressed against ones teeth and left in contact with the teeth for about 30 minutes. The plastic strip then is removed. The brush-on products are painted into teeth and the user keeping his/her mouth at least partially open for up to about a minute until the formulation dries onto the teeth. In both cases saliva will dilute and flush the tooth whitening composition from the user's teeth. This is more so with strips since foreign materials, such as a plastic strip, will enhance saliva flow in the mouth. These are useful products to remove some tooth staining. However, they are not as effective as the use of dental trays, and in particular the use of dental trays by dental professionals.
A problem with the various whitening compositions that are used in dental trays is that they are substantially soluble in water and saliva. This results in a dilution of the whitening formulation during use. In order to overcome this problem producers of these whitening formulations have increased the concentration of the whitening actives. However, this causes a problem of increased tooth sensitivity, gum irritation and the potential long term for lesions. Another solution disclosed in U.S. Pat. No. 5,846,058 has been to use higher viscosity tooth whitening compositions. This increases dilution time and flush time but is not a full solution to the problem. A better solution to this problem is to use a carrier and actives that are substantially insoluble in water and saliva, the carrier being about fully insoluble in water and saliva. The active must have some solubility in order to attack and remove tooth stains. However this should be at a low level. In this way tooth whitening compositions with a lower concentration of active can be used to enhance whitening through a longer contact time at a more sustained active concentration.